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Apart from the fuel that it consumes, there is one important liquid that your car’s engine needs—engine oil. But with cars getting better with successive generations, we, as owners, don’t really even have to look under the hood any more. As long as it is being serviced it should run fine, right?

But isn’t this taking things for granted? What if you’re being charged for unnecessarily expensive engine oil when it isn’t required? Should you continue to spend more money every oil change for no real benefit? How would you know the difference? Imagine the low oil warning lamp came on. Would you know what grade of oil to top up with? It’s not as easy as you’d imagine it. Read on to find answers to these and many other questions relating to this seemingly simple liquid.

An engine contains innumerable parts, mostly metal, that work together to produce power to move the car by burning fuel. These parts are made to withstand potentially destructive explosions within the engine’s confines created because of the continuous mixtures of air and fuel, and the resulting vibrations and heat that is generated. And the engine is expected to perform at its peak all the time. It’s the engine oil that protects these parts and lets them run smoothly.

The role

The main job of the oil is to lubricate the engine’s internals and keep the friction between them to a minimum. For example, pistons move to and fro at high speeds inside each of the engine’s cylinders and the greater the friction between the piston and the cylinder wall, the greater will be the energy required to overcome it. The engine oil forms a film between the metal parts to help them move freely. The oil also helps keep the temperatures in check as it absorbs the heat from the metal parts of the engine.

Then there’s the build up of hydrocarbon deposits within the engine because of the burning of fuel and the reaction with the impurities brought in by the air intake system. The oil also rids the engine of these (via the air filter) and keeps them away from the moving parts, thereby cleaning the engine. For this, there are some cleaning agents added to the oil as well.

Why change engine oil?

With use, the oil loses its lubrication properties and picks up bits of metal particles, and this leads to a decline in its performance.